The overall goal is to understand the chemistry of bridgehead intermediates and to apply this knowledge to the total synthesis of natural products. The specific goals include 1) the synthesis of the potent antitumor agent shikodonin; 2) the synthesis of colchicine and a heteroatom analog. Colchicine is an inhibitor of mitosis by affecting the action of microtubules; 3) the study of a rearrangement of a bridged ring system to a fused bicyclo(3.3.0) ring system. An immediate application is the antibiotic pentalenolactone E; and 4) the study of the cycloadditions of bridgehead enals with electron-rich alkenes. An immediate application is the isocedrene class of sesquiterpenes.